With the prior art, mechanical computer mice are typically specified to have a resolution of 400 dots per inch (dpi) and a maximum speed of 5 inches per second (ips), and may be tested before shipping to 7 ips. Some optical sensors within optical computer mice may be specified as having the same resolution as mechanical computer mice, but are capable of much higher speeds, such as speeds greater than 50 ips. Computer mice (both mechanical and optical), typically have resolution and speed limitation, in which no more than 7 bits of magnitude are needed to transmit the number of dots (Δx, Δy) counted during sampling intervals. For example, values from 0 through 127 can be represented in a 7-bit value and values in the range of −128 through 127 can be represented by a two's-complement value in 8 bits.
One particular prior art optical wireless computer mouse appears to send an 8 bit signed value (using a resolution of 800 dpi), indicating an amount of movement in each of a horizontal and vertical direction, via a radio frequency (RF) packet every 20 milliseconds, corresponding to a maximum mouse speed of about 8 ips. (50 RF packets per second (20 millisecond time intervals)×127 (maximum signed 8 bit value)×0.00125 inches per dot (800 dpi resolution) 7.9375 inches per second). Using a resolution of 400 dpi would yield a maximum speed of about 16 ips; however, the maximum tracking speed that a low speed USB device can support is 36 ips (at a 400 dpi resolution).
A ten-fold increase in speed, as may be attained by an optical mouse, means that displacement information (Δx, Δy data) could have a magnitude up to ten times larger than the magnitude for prior art mechanical mice. Therefore, 4 additional bits, or 11 bits, would be required to report such a magnitude and 12 bits would be required to report 11 bits of magnitude and a sign bit.
With a wireless pointer device, e.g., a wireless high-speed mouse, displacement information that conveys movement of the wireless pointer device is typically transmitted on a packet data stream over a radio frequency channel. Of course, the faster the wireless pointer device can transverse, the number of bits that may be required to represent the movement increases. However, a user interface that receives this information may be limited in the amount of information that can be processed. For example, with a universal serial bus (USB) interface, packets are sent approximately every 8 msec, where each packet has a time duration of 8 msec or less. If additional bits are required to be transported over an existing packet structure, an increase of the duration of a packet may be necessary. However, restructuring the packet structure is not desirable and may increase the time latency. Hence, there is a real need to send displacement information from a wireless high speed pointer device so that the time duration of transmitted packets are not increased while a resulting error is maintained within an acceptable amount.